Expanded beam fiber optic connector, and cable assembly, and methods for manufacturing

ABSTRACT

A fiber optic cable and connector assembly is disclosed. In one aspect, the assembly includes a cable optical fiber, an optical fiber stub and a beam expanding fiber segment optically coupled between the cable optical fiber and the optical fiber stub. The optical fiber stub has a constant mode field diameter along its length and has a larger mode field diameter than the cable optical fiber. In another aspect, a fiber optic cable and connector assembly includes a fiber optic connector mounted at the end of a fiber optic cable. The fiber optic connector includes a ferrule assembly including an expanded beam fiber segment supported within the ferrule. The expanded beam fiber segment can be constructed such that the expanded beam fiber segment is polished first and then cleaved to an exact pitch length. The expanded beam fiber segment can be fusion spliced to a single mode optical fiber at a splice location behind the ferrule.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a National Stage of PCT International Patentapplication No. PCT/US2014/047592, filed 22 Jul. 2014, which claimsbenefit of U.S. Patent Application Ser. No. 61/857,020 filed on Jul. 22,2013 and to U.S. Patent Application Ser. No. 61/857,015 filed on Jul.22, 2013, the disclosures of which are incorporated herein by referencein their entireties. To the extent appropriate, a claim of priority ismade to each of the above disclosed applications.

TECHNICAL FIELD

The present disclosure relates generally to optical fiber communicationsystems. More particularly, the present disclosure relates to fiberoptic connectors, fiber optic connector and cable assemblies and methodsfor manufacturing.

BACKGROUND

Fiber optic communication systems are becoming prevalent in part becauseservice providers want to deliver high bandwidth communicationcapabilities (e.g., data and voice) to customers. Fiber opticcommunication systems employ a network of fiber optic cables to transmitlarge volumes of data and voice signals over relatively long distances.Optical fiber connectors are an important part of most fiber opticcommunication systems. Fiber optic connectors allow two optical fibersto be quickly optically connected and disconnected.

A typical fiber optic connector includes a ferrule assembly supported ata front end of a connector housing. The ferrule assembly includes aferrule and a hub mounted to a rear end of the ferrule. A spring is usedto bias the ferrule assembly in a forward direction relative to theconnector housing. The ferrule functions to support an end portion of atleast one optical fiber (in the case of a multi-fiber ferrule, the endsof multiple fibers are supported). The ferrule has a front end face atwhich a polished end of the optical fiber is located. When two fiberoptic connectors are interconnected, the front end faces of theirrespective ferrules abut one another and the ferrules are forcedtogether by the spring loads of their respective springs. With the fiberoptic connectors connected, their respective optical fibers arecoaxially aligned such that the end faces of the optical fibers directlyoppose one another. In this way, an optical signal can be transmittedfrom optical fiber to optical fiber through the aligned end faces of theoptical fibers. For many fiber optic connector styles, alignment betweentwo fiber optic connectors is provided through the use of a fiber opticadapter that receives the connectors, aligns the ferrules andmechanically holds the connectors in a connected orientation relative toone another.

Connectors are typically installed on fiber optic cables in the factorythrough a direct termination process. In a direct termination process,the connector is installed on the fiber optic cable by securing an endportion of an optical fiber of the fiber optic cable within a ferrule ofthe connector. After the end portion of the optical fiber has beensecured within the ferrule, the end face of the ferrule and the end faceof the optical fiber are polished and otherwise processed to provide anacceptable optical interface at the end of the optical fiber.

Connectors can also be installed on fiber optic cables using an opticalsplice. The optical splice can be mechanical splice or a fusion splice.Mechanical splices are often used for field terminated connectors.Fusion splices can be used to fusion splice the optical fiber of thefiber optic cable to the rear end of an optical fiber stub securedwithin a ferrule. United States Patent Application Publication Pub. No.US 2014/0064665 A1 discloses example splice-on connector configurations.

What is needed are methods and structures for reducing signal loss atdemateable interfaces of fiber optic connectors.

SUMMARY

Teachings of the present disclosure relate to methods and structures forincreasing the fiber mode field diameter at the demateable interfacebetween two fiber optic connectors so as to reduce signal loss at theinterface.

One aspect of the present disclosure relates to a fiber optic cable andconnector assembly. The assembly includes a ferrule having a front endand a rear end, a cable optical fiber, an optical fiber stub having afirst and second portion and a beam expanding fiber segment opticallycoupled between the cable optical fiber and the optical fiber stub. Thesecond portion of the optical fiber stub projects rearwardly from therear end of the ferrule to be spliced. In one example, the optical fiberstub has a constant mode field diameter along its length and has alarger mode field diameter than the cable optical fiber.

Another aspect of the present disclosure relates to a fiber optic cableand fiber assembly. The assembly includes a ferrule having a front endand a rear end, an expanded beam fiber segment having a front portionsecured within the ferrule and a rear portion that projects rearwardlyfrom the rear end of the ferrule, and a fiber optic cable having asingle mode optical fiber optically coupled to the expanded beam fibersegment at a splice location behind the rear end of the ferrule.

A variety of additional aspects will be set forth in the descriptionthat follows. The aspects relate to individual features and tocombinations of features. It is to be understood that both the foregoinggeneral description and the following detailed description are exemplaryand explanatory only and are not restrictive of the broad inventiveconcepts upon which the embodiments disclosed herein are based.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of a fiber optic cable andconnector assembly in accordance with the principles of the presentdisclosure;

FIG. 2 is an enlarged view showing a ferrule hub and splice locationsfor the fiber optic cable and connector assembly of FIG. 1;

FIG. 3 is a schematic, longitudinal cross-sectional view showing themode field for an optical fiber structure of the fiber optic cable andconnector assembly of FIG. 1;

FIG. 4 is a schematic longitudinal cross-sectional view showing the modefield for an alternative optical fiber structure that can be used in thefiber optic cable and connector assembly of FIG. 1;

FIG. 5 is a cross-sectional view taken along section line 5-5 of FIG. 3;

FIG. 6 is a cross-sectional view taken along section line 6-6 of FIG. 3;

FIG. 7 is a cross-sectional view taken along section line 7-7 of FIG. 3;

FIG. 8 is a flow chart illustrating an example method in accordance withthe principles of the present disclosure for manufacturing the fiberoptic cable and connector assembly of FIG. 1;

FIG. 9 is a longitudinal cross-sectional view of a fiber optic cable andconnector assembly in accordance with the principles of the presentdisclosure;

FIG. 10 is a front, perspective, cross-sectional view of the fiber opticcable and connector assembly of FIG. 9;

FIG. 11 is a perspective view of a ferrule assembly in accordance withthe principles of the present disclosure;

FIG. 12 is a perspective view of fibers shown in the ferrule assembly ofFIG. 11;

FIG. 13 cross-sectional view of an expanding beam fiber segment shown inthe ferrule assembly of FIG. 12;

FIG. 14 a cross-sectional view of a single mode optical fiber shown inthe ferrule assembly of FIG. 12;

FIG. 15 is a perspective view of a ferrule assembly with an odd integer¼-pitch GRIN lens in accordance with the principles of the presentdisclosure;

FIG. 16 is a perspective view of a ferrule assembly with an even integer¼-pitch GRIN lens in accordance with the principles of the presentdisclosure; and

FIG. 17 is a flow chart illustrating a method for assembling a ferruleassembly in accordance with the principles of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates a fiber optic cable and connector assembly 20 inaccordance with the principles of the present disclosure. The fiberoptic cable and connector assembly 20 includes a fiber optic connector22 secured to the end of a fiber optic cable 24. The fiber opticconnector 22 includes a connector body 26 having a front end 28 and arear end 30. The fiber optic connector 22 also includes a ferruleassembly 32 mounted within the connector body 26. Ferrule assembly 32includes a ferrule 34 having a rear end supported within a ferrule hub36. A spring 38 biases the ferrule assembly 32 in a forward directionrelative to the connector body 26. The fiber optic connector 22 alsoincludes a release sleeve 40 that is mounted over the connector body 26that can be pulled-back relative to the connector body to release thefront end 28 of the connector body 26 from a corresponding fiber opticadapter. The fiber optic cable 24 is shown including an outer jacket 42that encloses a cable optical fiber 44 positioned within a protectivebuffer 46 (e.g., a buffer layer such as a loose buffer layer, a tightbuffer layer or a loose/tight buffer layer). The fiber optic cable 24also includes a strength layer 48 (e.g., aramid yarn or another type oftensile reinforcing material) positioned between the buffer tube 46 andthe outer jacket 42. The strength layer 48 is shown anchored (e.g.,crimped) to the rear end 30 of the connector body 26. The fiber opticconnector 22 includes a tapered boot 50 that provides strain reliefand/or fiber bend radius protection at the interface between the fiberoptic connector 22 and the fiber optic cable 24.

Referring to FIG. 2, the fiber optic connector 22 includes a fiberstructure 52 that is optically coupled (e.g., spliced) to the cableoptical fiber 44. The fiber structure 52 includes an optical fiber stub54 secured (e.g., adhesively affixed) within a longitudinal bore 56 ofthe ferrule 34. The optical fiber structure 52 also includes a beamexpanding fiber segment 58 positioned between the cable optical fiber 44and the optical fiber stub 54. The beam expanding fiber segment 58 isconfigured for expanding light beams traveling in a direction from thecable optical fiber 44 toward the optical fiber stub 54 and for focusinglight beams traveling in a direction from the optical fiber stub 54toward the cable optical fiber 44. The optical fiber stub 54 can includea construction for maintaining a constant mode field diameter along alength of the optical fiber stub 54. It will be appreciated that thephrase “constant mode field diameter along a length of the optical fiberstub” means that the mode field diameter is generally constant along thelength of the optical fiber stub and includes embodiments where minorvariations in diameter that do not have a meaningful impact on opticalsignals passing therethrough are present.

As used herein, “mode field” means the portion of an optical fiberthrough which light passes during a transmission through the opticalfiber of a light signal having a predetermined wavelength. It will beappreciated that the “mode field” of a given optical fiber may varydepending upon the wavelength of the light signal being transmittedtherethrough. As used herein, the “mode field area” is the transversecross-sectional area of the mode field at a given location of theoptical fiber. The “mode field area” is typically circular and defines amode field diameter across the mode field area. The mode field diametercan be defined as where the power density is reduced to 1/e² of themaximum power density. The mode field area can also be referred to as a“spot area” or “beam area” and the mode field diameter can also bereferred to as the spot size or beam width.

It will be appreciated by those of skill in the art that the fiber opticconnector 22 depicted at FIG. 1 is an SC style connector. It will beappreciated that the various aspects of the present disclosure are alsoapplicable to other types of connectors having different form factors.Example other types of connectors include LC connectors, ST connectors,or ruggedized/hardened connectors of the type disclosure at U.S. Pat.Nos. 7,744,286 and 7,090,407 which are hereby incorporated by reference.

Referring again to FIG. 1, the ferrule 34 can be positioned at leastpartially within the connector body 26 adjacent the front end 28 of theconnector body 26. As shown at FIG. 2, the ferrule 34 includes a frontend 60 positioned opposite from a rear end 62. The front end 60 includesan end face 64 at which an interface end 66 of the optical fiber stub 54is located. The longitudinal bore 56 of the ferrule 34 extends throughthe ferrule 34 from the front end 60 to the rear end 62. The opticalfiber stub 54 includes a first portion 68 and a second portion 70. Thefirst portion 68 can be secured within the longitudinal bore 56 of theferrule 34 and the second portion 70 can extend rearwardly from theferrule 34. The first portion 68 of the optical fiber stub 54 ispreferably secured by an adhesive (e.g., epoxy) within the longitudinalbore 56 of the ferrule 34. The interface end 66 of the optical fiberstub 54 can include a polished end face accessible at the front end 60of the ferrule 34. The optical fiber stub 54 can extend all of the waythrough the ferrule 34 without any splices within the ferrule 34.

In one example, the optical fiber stub 54 has a construction designedand configured to maintain a constant mode field diameter along itslength. In one example, the optical fiber stub 54 is a step-indexoptical fiber having a core 200 (see FIG. 3) surrounded by a cladding202 (see FIG. 3) with a discrete radial step in refractive index betweenthe core and the cladding. In certain examples, the optical fiber stub54 is designed to inhibit the excitation of multiple transmission modesover a predetermined range of wavelengths (e.g., 1260-1650 nanometers).Thus, the stub 54 supports only a single fundamental mode over thepredetermined range of wavelengths. In certain examples, the opticalfiber stub 54 has a core diameter greater than 10 micrometers, orgreater than 12 micrometers, or greater than 20 micrometers, or greaterthan 30 micrometers, or greater than 40 micrometers, or greater than 50micrometers. In other examples, the optical fiber stub 54 has a corediameter within the range of 50 to 100 micrometers. In other examples,the optical stub fiber 54 has a core diameter in the range of 10 to 125micrometers. In still other examples, the optical fiber stub 54 can havea cladding having an outer diameter in the range of 120 to 130micrometers.

Referring to FIG. 2, the longitudinal bore 56 of the ferrule 34 can havea stepped diameter. For example, the longitudinal bore 56 can have afirst diameter d1 that is larger than a second diameter d2. The firstdiameter d1 can be positioned at the front end of the ferrule 34 and thesecond diameter d2 can be positioned adjacent the rear end of theferrule 34. In certain examples, the portion of the optical fiber stub54 within the section of the longitudinal bore 56 having the firstdiameter d1 can be protected by a protective coating acrylate or otherpolymeric material) and the portion of the optical fiber stub 54 withinthe section of the longitudinal bore 56 having the second diameter d2includes bare glass (i.e., a glass core and cladding that is notsurrounded by a protective coating).

In certain examples, the cable optical fiber 44 is a step-index opticalfiber having a core 204 (see FIG. 3) surrounded by a cladding 206 (seeFIG. 3). In a step index optical fiber, a discrete step in refractiveindex is provided radially between the core and the cladding. In oneexample, the cable optical fiber 44 functions as a single mode opticalfiber and supports a single fundamental transmission mode for lighttransmissions having wavelengths in the predetermined wavelength range(e.g., 1260-1650 nanometers) specified with respect to the optical fiberstub 54. In certain examples, the cable optical fiber 44 has a corediameter in the range of 5 to 15 micrometers, or in the range of 8 to 12micrometers, or of about 10 micrometers. In certain examples, the cableoptical fiber 44 can be configured to accommodate multi-mode opticaltransmissions. Portions of the cable optical fiber 44 can be protectedby a coating 57 (e.g., acrylate or other polymeric material) thatsurrounds the cladding layer.

It is preferred for the core diameter of the optical fiber stub 54 to belarger than the core diameter of the cable optical fiber 44 (e.g., atleast 50% larger). In certain examples, the core diameter of the opticalfiber stub 54 is at least two times, three times, four times, fivetimes, six times, seven times, eight times, nine times or ten times aslarge as the core diameter of the cable optical fiber 44. It ispreferred for the mode field diameter of the optical fiber stub 54 to belarger than the mode field diameter of the cable optical fiber 44 (e.g.,at least 50% larger). In certain examples, the mode field diameter ofthe optical fiber stub 54 is at least two times, three times, fourtimes, five times, six times, seven times, eight times, nine times orten times as large as the mode field diameter of the cable optical fiber44.

As described above, in certain examples, the beam expanding fibersegment 58 of the optical fiber structure 52 can be configured to expanda light beam traveling in a first direction through the beam expandingfiber segment 58 and to focus a light beam traveling in an oppositesecond direction through the beam expanding fiber segment 58. In certainexamples, the beam expanding fiber segment 58 can include a collimatorfor expanding/focusing light including, for example, a lens or anexpanded core of a fiber, in particular, a thermally-expanded core. Incertain examples, the beam expanding fiber segment 58 can include a lenssuch as a graded index (GRIN) lens. In a preferred example, the beamexpanding fiber segment 58 can include a quarter pitch GRIN lens. Incertain examples, the beam expanding fiber segment 58 can include agraded-index optical fiber having a core having a generally parabolicfiber refractive index profile that has a maximum value at the center ofthe core and that gradually decreases as the core extends radially awayfrom the center of the core. It will be appreciated that the beamexpanding fiber segment 58 functions to provide a gradual transition inmode field diameter between the cable optical fiber 44 and the opticalfiber stub 54 (see FIG. 3 where the mode fields are the darkenedportions of the fiber segments).

Referring to FIG. 3, an example mode field configuration for the opticalfiber structure 52 is depicted. As shown at FIG. 3, the beam expandingfiber segment 58 is a GRIN lens that is spliced between the cableoptical fiber 44 and the optical fiber stub 54 so as to provide anoptical coupling between the cable optical fiber 44 and the opticalfiber stub 54. For example, the beam expanding fiber segment 58 isspliced to the cable optical fiber 44 at splice location 72 and the beamexpanding fiber segment 58 is spliced to the optical fiber stub 54 atsplice location 74. In a preferred example, the splice locations 72, 74are positioned inside the ferrule hub 36 such that the ferrule hub 36protects and encloses the splice locations 72, 74. It will beappreciated that at the time of splicing, the beam expanding fibersegment 58 can include a bare glass section of graded index fiber, andthe ends of the cable optical fiber 44 and the optical fiber stub 54 canalso be bare glass (i.e., uncoated glass). After splicing, a protectivebuffer layer 76 can be provided over the splice locations 72, 74 andover the beam expanding fiber segment 58. Thereafter, the ferrule hub 36can be positioned (e.g., over molded) over the rear end of the ferrule34 and over the optical fiber structure 52. In this way, the secondportion 70 of the optical fiber stub 54, the beam expanding fibersegment 58, an end portion of the cable optical fiber 44 and the rearend of the ferrule 34 can all be contained within the ferrule hub 36.The spring 38 can abut against the ferrule hub 36 to bias the ferruleassembly 32 in the forward direction.

Referring still to FIG. 3, the beam expanding fiber segment 58 providesa gradual transition in mode field diameter from the smaller core of thecable optical fiber 44 to the larger core of the optical fiber stub 54.FIG. 5 shows a mode field area 208 of the cable optical fiber 44 havinga mode field diameter D1. FIG. 7 shows a larger mode field area 210 ofthe optical fiber stub 54 having a mode field diameter D2. FIG. 6 showsa mode field area 212 provided by the beam expanding fiber segment 58 ata location about half way along the length of the beam expanding fibersegment 58. The mode field area 212 has a mode field diameter D3.

In the depicted example, splice location 74 is spaced rearwardly fromthe rear end of the ferrule 34. In certain examples, the splice location74 is positioned no more than 20 millimeters from the rear end of theferrule 34. In still other examples, the splice location 74 ispositioned 5 millimeters or less from the rear end of the ferrule 34. Insome examples, the first and second splice locations 72, 74 are fusionsplices. The splice locations 72, 74 can include factory fusion splice.A “factory fusion splice” is a splice performed at a manufacturingfacility as part of a manufacturing process. In certain examples, anactive alignment system is used to align the fiber sections prior tosplicing. In still other examples, the splices can be a field splices.

FIG. 4 shows an alternative optical fiber structure 52 a that can beused in the fiber optic connector 22. The optical fiber structure 52 aincludes a two-piece beam expanding fiber segment 58 a. The two-piecebeam expanding fiber segment 58 a includes a pre-expansion fiber 78 anda primary beam expanding fiber 80 joined at a splice 82. Similar to thepreviously subscribed example, the two-piece beam expanding fibersegment 58 a is optically coupled between the cable optical fiber 44 andthe optical fiber stub 54. The pre-expansion fiber 78 and the primarybeam expanding fiber 80 cooperate to expand light beams traveling fromthe cable optical fiber 44 to the optical fiber stub 54 and to focuslight beams traveling from the optical fiber stub 54 to the cableoptical fiber 44.

Referring back to FIG. 1, the connector body includes a front piece 120and a rear piece 122. The front piece 120 forms the front interface end28 of the fiber optic connector 22 and the rear piece 122 is configuredto allow the strength layer 48 (e.g., aramid yarn, fiberglass or otherstrength members capable of providing tensile reinforcement to the fiberoptic cable 24) of the fiber optic cable 24 to be anchored. In someexamples, the strength layer 48 can be secured to the rear piece 122 ofthe connector body 26 with a mechanical retainer such as a crimpedsleeve. In other examples, adhesive or other means can be used to securethe strength layer 48 to the connector body 26.

The front and rear pieces 120, 122 of the connector body 26 caninterconnect the other by connection such as a snap fit connection, anadhesive connection or other type of connection. When the front and rearpieces 120, 122 are connected together, the spring 38 and the ferrulehub 38 are captured between the front and rear pieces 120, 122. The hub36 can be shaped to include a flange 160 that engages the spring 38.Additionally, the hub 36 can be configured to support the rear end ofthe ferrule 34 within the connector body 26. Furthermore, a forward endof the flange 160 can be configured to engage a shoulder 161 within theconnector body 26 to halt forward movement of the ferrule assembly 32caused by the forward bias of the spring 38. The spring 38 can becaptured within a spring pocket 162 defined by the rear piece 122 and,as described above, can function to bias the ferrule assembly 32 in aforward direction relative to the connector body 26. The hub 36 is astructure secured on the ferrule 34 such that the ferrule 34 and the hub36 move together as a unit relative to the connector body 26. Asdescribed above, the hub 36 can include structure that interferes withan internal structure (e.g., a stop) of the connector body 26 to limitthe forward movement of the ferrule assembly 32 and to prevent theferrule assembly 32 from being pushed out the front end of the connectorbody 26 by the spring 38.

As described above, the fiber optic connector 22 is shown having anSC-type intermatability profile. As such, the fiber optic connector 22can be adapted to be received within an SC-type fiber optic adapter thatis used to couple two of the connectors together to provide an opticalconnection thereinbetween. When the fiber optic connector 22 is insertedwithin a fiber optic adapter, exterior shoulders of the connector body26 are engaged by latches of the fiber optic adapter to retain the fiberoptic connector 26 within the fiber optic adapter. To release the fiberoptic connector 22 from the adapter, the release sleeve 40 is slidrearwardly relative to the connector body 26 thereby causing the latchesof the fiber optic adaptor to disengage from the exterior shoulders ofthe connector body 26 such that the fiber optic connector 22 can bewithdrawn from the fiber optic adapter. An example fiber optic adaptoris disclosed at U.S. Pat. No. 5,317,663 which is hereby incorporated byreference in its entirety.

As described above, the beam expanding fiber segment 58 can include agraded index lens (GRIN). A GRIN lens is made with a refractive indexthat varies parabolically as a function of the radius. The amount ofexpansion provided by the GRIN lens is dependent upon its constructionand length. Typically, maximum expansion is achieved at multiples of thequarter pitch of the GRIN lens. As indicated above, the amount ofexpansion provided by the GRIN lens is dependent upon its configurationand length. By using the optical fiber stub 54 in combination with thebeam expanding fiber segment 58, the beam expanding fiber segment 58 canbe precisely controlled to achieve a desired level of expansion. Theinterface end 66 of the optical fiber stub 54 can be polished in aconventional fashion to produce conventional end face geometry such as,but not limited to, straight, flat, curved or slanted configurationswithout modifying the length and degree of expansion provided by thebeam expanding fiber segment 58. The larger mode field diameter providedthrough the cooperation of the beam expanding fiber segment 58 and theoptical fiber stub 54 reduces the importance of precise co-axialalignment at the connector to connector interface. The ferrule 34 can beconstructed of a relatively hard material capable of protecting andsupporting the first portion 68 of the optical fiber stub 54. In oneexample, the ferrule 34 has a ceramic construction. In other examples,the ferrule 34 can be made of alternative material such as UItem,thermoplastic material such as polyphenylene, sulfide (PPS), or otherengineering plastics or metals. In certain examples, the ferrule 34 canhave a longitudinal length in the range of 5-15 millimeters.

In some examples, the hub 36 can have a polymeric construction that hasbeen overmolded over the rear end of the ferrule 34 and over the splicelocations (e.g., splice locations 72 and 74 or splice locations 72, 74and 80). Additionally, in certain examples, the overmolded hub 36 can beformed of a hot melt adhesive or other material that can be applied andcured at relatively low molding temperatures and pressures. The ferrulehub 36 can also be formed from a UV curable material (i.e., materialsthat cure when exposed to ultraviolet radiation/light), for example, UVcurable acrylates, such as OPTOCAST™ 3761 manufactured by ElectronicMaterials, Inc. of Breckenridge, Colo.; ULTRA LIGHT-WELD® 3099manufactured by Dymax Corporation of Torrington, Conn.; and 3M™Scotch-Weld™ manufactured by 3M of St. Paul, Minn. The use of UV curablematerials is advantageous in that curing can occur at room temperatureand at generally lower pressures (e.g., less than 30 kpsi, and generallybetween 20-30 kpsi). The availability of low pressure curing helps toinsure that the components, such as the optical fibers, being overmoldedare not damaged during the molding process. By protecting the spliceswithin the hub at a location in close proximity to the ferrule 36, it ispossible to manufacture a fiber optic connector that is relatively shortin length. Providing one or more of the splice locations within 5millimeters of the rear end of the ferrule 34 assists in designing thefiber optic connection in compliance with standard industry for customerside load and connector length specifications (e.g., GR-326 size loadand length requirements).

FIG. 8 is a flow chart illustrating an example method 150 formanufacturing the fiber optic cable and connector assembly 20. In thisexample, the method 150 includes operations 152, 154, 156, 158, 160,162, 164 and 166.

The operation 152 is performed to secure the optical fiber stub 54 inthe ferrule 74. As previously described, the optical fiber stub 54 canbe adhesively secured within the bore of the ferrule 34.

The operation 154 is performed to polish the end face 64 of the ferrule34 and the corresponding interface end 66 of the optical fiber stub 54secured within the ferrule 34. The end face of the interface end 66 ofthe optical fiber stub 54 can be polished having a desired geometry.

The operation 156 is performed to cleave the rear end of the opticalfiber stub 54. In one example, after cleaving, the rear end of theoptical fiber stub 54 can be within 5 millimeters of the rear of theferrule 34.

The operation 158 is performed to splice the beam expanding fibersegment 58 the rear end of the optical fiber stub 54. In anotherexample, beam expanding fiber segment 58 a can be spliced to the opticalstub fiber instead of the beam expanding fiber segment 58.

The operation 160 is performed to cleave the beam expanding fibersegment 58 to a controlled length. The length of the beam expandingfiber segment 58 can be controlled to achieve a desired amount ofexpansion. Both ends of the beam expanding fiber segment 58 can becleaved prior to splicing to the optical fiber stub 54, or one end ofthe beam expanding fiber segment 58 can be cleaved after splicing to thefiber optic stub 54. In the case of the expanding fiber segment 58 a,the pre-expansion fiber 78 and the primary expansion fiber 80 can becleaved to desired lengths, spliced together and then the primaryexpansion fiber 80 can be spliced to the optical fiber stub 54. Ofcourse, the order of splicing can be varied such that the primaryexpansion fiber 80 is first spliced to the optical fiber stub 54 andthen spliced to the pre-expansion fiber 78.

The operation 162 then is performed to splice the beam expanding fibersegment 58 to the cable optical fiber 44. In another embodiment, thebeam expanding fiber segment 58 a is spliced to the cable optical fiber44 by splicing the pre-expansion fiber 78 to the cable optical fiber 44.

The operation 164 is performed to install the ferrule hub 36 over therear end of the ferrule 34 and over the splice locations. The ferrulehub 36 can contain and protect the beam expanding fiber segment 58, 58 aand the various splices used to couple the beam expanding fiber segment58, 58 a between the optical fiber stub 54 and the cable optical fiber44.

The operation 166 is performed to install the ferrule assembly 32 in theconnector body 26. In certain embodiments, the rear connector piece 122and the spring have been slid over the cable optical fiber 44 prior toover molding the hub. In this step, the ferrule assembly 32 is loadedinto the front piece 120, the spring is slid from the cable opticalfiber 44 to a position behind the hub and within the front connectorpiece 120, and the rear connector piece is slid forwardly from the cableoptical fiber 44 into engagement with the front connector piece 122thereby capturing the hub and the spring between the front and rearconnector pieces 120, 122.

Another aspect of the present disclosure relates to a method for massproducing and distributing fiber optic connector assemblies. One aspectof the method relates to the centralized manufacturing of largequantities of ferrules having optical fiber stubs mounted therein. Theoptical fiber stubs can be of the type described herein and can includerelatively large mode field diameters. In certain examples, the volumeof the ferrule and stub combinations manufactured at a given centralizedlocation can exceed a volume of 500,000; 1,000,000; 2,000,000; or3,000,000 per year. The ferrule and stub combinations can bemanufactured in a first factory location using highly precise polishingtechnology and equipment. The first factory location can be used tomanufacture the ferrule and stub assemblies according to methodoperations 152-154 such that the ferrule assemblies manufactured at thecentral location each include a ferrule 34 and an optical fiber stub 54of the type described herein having a constant mode field diameter alongits length.

The method also leads to distributing the ferrule and stub assembliesmanufactured at the first factory location to regional factories/massproduction locations closer to the intended point of sales. Duringshipping of the ferrule and stub assemblies, the rear portions 70 of theoptical fiber stubs 54 can be coated with a protective coating layer(e.g., acrylate) to provide protection during transit, and or coveredwith a protective cap secured to the back end of the ferrule. Similarly,dust caps can be proved over the front ends of the ferrules 34. Theultimately small size of the ferrule and stub fiber assemblies allowslarge, large volumes of such ferrule and stub fiber assemblies to beeffective shipped at relatively low cost. High costs associated withextensive shipment of cable can be significantly reduced. At theregional locations, the protective coatings can be stripped from thefiber stubs and operations 156-166 can be performed at the regionalfactory locations to splice the expansion fibers 58, 58 a to the opticalfiber stubs 54 and to splice the expansion fibers 58, 58 a to the cableoptical fibers 44.

In other embodiments, steps 152-160 can be performed at the centralmanufacturing location. Once the optical fiber stubs 54 have beenprocessed with the ferrules 34 and the beam expansion fiber 58, 58 ahave been spliced to the optical fiber stubs, protective caps (e.g.,dust caps, can be placed over the front and rear ends of the ferrules toprotect the interface ends 66 of the optical fiber stubs 54 as well asthe expansion fibers 58 or 58 a and their corresponding splices.Thereafter, the protected ferrule assemblies can be shipped to regionallocations for final assembly on a cable (e.g., steps 162-166).

FIGS. 9-10 show another example of a fiber optic cable and connectorassembly 300 in accordance with the principles of the presentdisclosure. The fiber optic cable and connector assembly 300 includes afiber optic connector 302 secured to the end of a fiber optic cable 354.The fiber optic connector 302 includes a connector body 304 having afront end 306 and a rear end 308. The fiber optic connector 302 alsoincludes a ferrule assembly 420 mounted within the connector body 304.Ferrule assembly 420 includes a ferrule 422 having a rear end 428supported within a ferrule hub 464. A spring 318 biases the ferruleassembly 420 in a forward direction relative to the connector body 304.The fiber optic connector 302 also includes a release sleeve 328 that ismounted over the connector body 304 that can be pulled-back relative tothe connector body to release the front end 306 of the connector body304 from a corresponding fiber optic adapter. The fiber optic cable 354is shown including an outer jacket 358 that encloses a cable opticalfiber 356 positioned within a protective buffer 362 (e.g., a bufferlayer such as a loose buffer layer, a tight buffer layer or aloose/tight buffer layer).

In this example, the cable optical fiber 356 functions as a single modeoptical fiber for light transmissions having wavelengths in the range1310 to 1550 nanometers. In certain examples, the cable optical fiber356 is a step-index optical fiber. In a step index optical fiber, adiscrete step in refractive index is provided radially between the coreand the cladding. The fiber optic cable 354 also includes a strengthlayer 348 (e.g., aramid yarn or another type of tensile reinforcingmaterial) positioned between a buffer tube 360 and the outer jacket 358.The strength layer 348 is shown anchored (e.g., crimped) to the rear end308 of the connector body 304. The fiber optic connector 302 includes atapered boot 310 that provides strain relief and/or fiber bend radiusprotection at the interface between the fiber optic connector 302 andthe fiber optic cable 354.

Referring to FIGS. 11-12 an example mode field configuration for anexpanded beam fiber segment 424 is depicted. The expanded beam fibersegment 424 is a GRIN lens that is spliced to optical fiber 446 atsplice location 448 so as to provide an optical coupling between theoptical fiber 446 and the expanded beam fiber segment 424. In oneexample, the splice location 448 can be behind the rear end 428 of theferrule 422. In providing this construction, the mode field diameter ofthe optical fiber 446 can be increased to any desired diameter. Thisarrangement has the advantage of providing for less sensitivity tolateral and longitudinal fiber core misalignment and less sensitivity tothe contamination and defects of the fiber.

In certain examples, the splice location 448 can be positioned no morethan 20 mm from the rear end 428 of the ferrule 422. In other examples,the splice location 448 can be positioned 5 mm or less from the rear end428 of the ferrule 422. In some examples, the splice location 448 is afusion splice. The splice location 448 can be a factory fusion splice. A“factory fusion splice” has been previously defined above. Accordingly,the description and features of such are also applicable in thisexample.

The fiber optic connector 302 includes the expanded beam fiber segment424 secured (e.g., adhesively affixed) within a longitudinal bore 334 ofthe ferrule 422. The expanded beam fiber segment 424 is configured forexpanding light beams traveling in a direction from the cable opticalfiber 356 toward the expanded beam fiber segment 424 and for focusinglight beams traveling in a direction from the expanded beam fibersegment 424 toward the cable optical fiber 356. The expanded beam fibersegment 424 can include a construction for expanding a mode fielddiameter along a length of the expanded beam fiber segment 424.

The expanded beam fiber segment 424 can be referred to as a “GRIN lens.”The typical length of GRIN lens is about 300 micrometers depending onthe requirements. This length typically corresponds to one quarterpitch. GRIN lens typically has a length tolerance of about ±10micrometers. An example expanded beam fiber is disclosed at U.S. Pat.No. 7,031,567, which is hereby incorporated by reference in itsentirety. Maximum expansion achieved at the multiple of quarter pitch ofGRIN lens.

Referring again to FIG. 11, the ferrule 422 can include a front end 426positioned opposite from a rear end 428. The front end 426 preferablyincludes an end face 430 at which an interface end 432 of the beamexpanded fiber segment 424 is located. The expanded beam fiber segment424 includes a first portion 438 that can be positioned within theferrule and extend therethrough from the front end 426 to the rear end428 of the ferrule 422. The expanded beam fiber segment 424 can furtherinclude a second portion 440 that resides outside the ferrule 422. Thefirst portion 438 can be secured within the ferrule 422 and the secondportion 440 can extend rearwardly from the ferrule 422. The firstportion 438 of the expanded beam fiber segment 424 can be secured by anadhesive (e.g., epoxy) within the ferrule bore 334 of the ferrule 422.The interface end 432 preferably includes a polished end face 430accessible at the interface end 432 of the ferrule 422. The expandedbeam fiber segment 424 can extend all the way through the ferrule 422without any splices within the ferrule 422.

Referring again to FIG. 9, the concepts and features of the connectorbody 304 and hub 464 are similar to the connector body 26 and hub 36described above in FIG. 1. As such, the description for the connectorbody 26 and hub 36 are hereby incorporated by reference in theirentirety for the connector body 304 and hub 464. In certain embodiments,the hub 464 provides structure against which the bias of the spring 318can be applied to bias the hub 464 and the ferrule 422 forwardlyrelative to the connector body 304. The boot 310, the rear piece 314 andthe spring 318 all can have internal dimensions (e.g., inner diameters)larger than an outer dimension (e.g., an outer diameter) of the cable354 such that during assembly/manufacturing the boot 310, the rear piece314 and the spring 318 can be slid back over the jacket 358 to providespace/clearance for splicing and application of the hub 464.

Referring to FIGS. 13-14, the expanded beam fiber segment 424 has afirst mode field diameter D4 and the expanded beam fiber segment 424 hasa second mode field diameter D5. The expanded beam fiber segment 424provides an expansion of the mode field diameter from the smaller modefield diameter D4 of the optical fiber 446 to the larger mode fielddiameter D5 of the expanded beam fiber segment 424. FIG. 13 shows a modefield area 366 of the expanded beam fiber segment 424 with the firstmode field diameter D4. FIG. 14 shows a smaller mode field area 368 ofthe optical fiber 446 with the second mode field diameter D5. In thisexample, the first mode field diameter D4 can be at least two times aslarge as the second mode field diameter D5. In other examples, the firstmode field diameter D4 can have a diameter expansion from about 20micrometers up to about 125 micrometers. The expanded beam fiber segment424 can convert the mode field of an optical signal of the optical fiber446 to be significantly greater by expanding the second mode fielddiameter D5 up to a desired expansion.

As shown in FIGS. 12 and 14, the optical fiber 446 can have a coreregion 450 surrounded by a cladding region 352. In some examples, thecore region 450 of the optical fiber 446 can have a diameter in therange of about 8 micrometers to about 12 micrometers. In other examples,the cladding region 352 of the optical fiber 446 can have an outerdiameter of about 125 micrometers. The optical fiber 446 can beoptically coupled to the fiber optic cable 354.

It will be appreciated that the beam expanding fiber segment 354functions to provide an expansion in mode field diameter between theoptical fiber 446 and the expansion beam fiber segment 424 (see FIG. 12where the mode fields are the darkened portions of the fiber segments).

Referring to FIG. 15, the expanded beam fiber segment 424 is depictedwithin a ferrule 422. Due to the parabolic shape of the expanded beamfiber segment 424, the modal fields that can travel in the expanded beamfiber segment have different propagation coefficients, but are evenlydistributed with respect to each other. As such, the constructive anddestructive interference of the near-field is of periodic nature. Inthis example, the expanded beam fiber segment 424 has an odd integer ¼pitch length L₁. A ¼ pitch length is about 3 micrometers. The “pitch” Pof the lens is the fraction of a full sinusoidal period that the raytraverses in the lens (i.e., a lens with a pitch of 0.25 has a lengthequal to ¼ of a sine wave, which would collimate a point source at thesurface of the lens). The expanded beam fiber segment 424 is nicelycollimated at the interface end 432 of the ferrule 422 by exploiting theperiodicity of the interfering modal fields in the expanded beam fibersegment 424. This provides for the desired selection of an integermultiple of the original expanded beam fiber segment 424 length. Theexpanded beam fiber segment 424 is a ¼ pitch, so that the optical fieldis expanded. A ½ pitch (2 quarter pitches) gives an intermediate focus F(see FIG. 16). Therefore, the odd integer multiple shown in FIG. 15provides for the maximum expanded beam.

Referring to FIG. 16 the expanded beam fiber segment 424 is depictedwithin the ferrule 422. In this example, the expanded beam fiber segment424 has an even integer ¼ pitch length L₁. The even integer multipleprovides for an imaging lens or (focused) field. The even-integermultiple of the pitch GRIN lens can be constructed to maintainpolarization focus or expand. In some examples, the expanded beam fibersegment 424 can be larger than the ferrule 422 if the integer multipleis large enough. The expanded beam fiber segment 424 expand light beamstraveling from optical fiber 446 to the expanded beam fiber segment 424and to focus light beams traveling from the expanded beam fiber segment424 to the optical fiber 446.

In some examples, the expanded beam fiber segment 424 can have at leasttwo pitch lengths. In other examples, the expanded beam fiber segment424 can have at least 3 pitch lengths. In another example, the expandedbeam fiber segment 424 can have at least one pitch length and an eveninteger of quarter pitches. In another example, the expanded beam fibersegment 424 can have at least one pitch length and an odd integer ofquarter pitches. Still in other examples, the expanded beam fibersegment 424 can have a pitch length that is longer or shorter than aquarter pitch such that expansion can be tuned to achieve a desired modefield diameter. Therefore, the mode conversion can be done by givingmore area around even number of pitches such that the pitch length canbe shorter or longer. This can help to tune the expanded beam fibersegment 424 to a mating fiber or tune it in light of an air gap. Thisarrangement eliminates the need to have an exact ¼ pitch. It is to beunderstood that the pitch length may vary with other examples.

Turning again to FIG. 11 the loose buffer tube 360 (i.e. furcation tube)can surround and protect at least a portion of the optical fiber 356.The buffer layer 362 can be affixed or otherwise bonded to the exteriorsurface of the buffer tube 360 and also can fill a portion of the buffertube 360 so as to bond with an interior surface of the buffer tube 360.The buffer layer 362 projects rearwardly beyond a rearward end of a hub464. In this way, the rearward end of the hub 464 can circumferentiallysurround and contact the buffer layer 362 but does not contact thebuffer tube 360. Thus, a mold for forming the hub 464 can be configuredto shut-off around the buffer layer 362 rather than the buffer tube 360.In some examples, the buffer layer 362 has an outer diameter larger thanan outer diameter of the buffer tube 360.

In the depicted example, the fiber optic connector 302 is shown as astandard SC-type connector. The concepts and features of the fiber opticconnector 302 are similar to the fiber optic connector 22 describedabove. As such, the description for the fiber optic connector 22 ishereby incorporated by reference in its entirety for the fiber opticconnector 302.

After the fusion splice has been completed, a protective layer 330 canbe placed, applied or otherwise provided over the optical fibers 446,356 in the region between the rear end 428 of the ferrule 422 and abuffered/coated portion of the optical fiber 356. The fiber opticconnector 302 fully complies with Telcordia GR-326 or similar stringentindustry or customer specifications.

The ferrule 422 can be constructed of a relatively hard material capableof protecting and supporting the first portion 438 of the expanded beamfiber segment 424. The concepts and features of the ferrule 422 aresimilar to the ferrule 34 described above. As such, the description forthe ferrule 34 is hereby incorporated by reference in its entirety forthe ferrule 422.

FIG. 17 is a flow chart illustrating an example method 500 formanufacturing a ferrule assembly including the ferrule 422 and theexpanded beam fiber segment 424 (i.e. GRIN lens). In this example, themethod 500 includes operations 502, 504, 506, 508, 510, and 512.

The operation 502 is performed to secure the expanded beam fiber segment424 (i.e. GRIN lens) in the ferrule 422. An arbitrary length can be usedto glue the expanded beam fiber segment 424 in the ferrule 422. Anexample of the expanded beam fiber segment 424 (i.e. GRIN lens) is shownand described with reference to FIGS. 9-11.

The operation 504 is performed to polish an end of the ferrule 422 andan end of the expanded beam fiber segment 424. The Examples of theferrule 422 and the expanded beam fiber segment 424 (i.e. GRIN lens) areshown and described in FIG. 9.

The operation 506 is performed to cleave the expanded beam fiber segment424 (i.e. GRIN lens) to a controlled pitch length. The selection can bemade to achieve a specific amount of expansion.

The operation 508 is performed to splice the expanded beam fiber segment424 (i.e. GRIN lens) to a single mode optical fiber 446. An example ofthe single mode optical fiber 446 is illustrated and described in moredetail in FIGS. 9-10.

The operation 510 is performed to install the hub 464 over the ferrule422. An example of the hub 464 is illustrated and described in moredetail in FIG. 9.

The operation 512 is performed to install the ferrule 422 in theconnector body 304. An example of the connector body 304 is illustratedand described in more detail in FIGS. 15-16.

Another aspect of the present disclosure relates to a method for massproducing and distributing fiber optic connector assemblies. Forexample, ferrule assemblies can be manufactured in a first factorylocation using the highly precise polishing technology and equipment.The first factory location can be used to manufacture the ferruleassembly according to method operations 502-506. By manufacturing suchlarge volumes of ferrule assemblies at one centralized location, theferrule assemblies can be made efficiently and considerable capitalinvestment can be made in premium quality manufacturing equipment andprocesses.

The method also relates to distributing ferrule assemblies manufacturedat a second location to regional factories/mass production locationscloser to the intended point of sales. The relative small size offerrule assemblies allows large volumes of such ferrule assemblies to beeffectively shipped at relatively low costs. High costs associated withextensive shipment of cable can be significantly reduced. The methodoperations 508-512 can be performed at regional factories/massproductions closer to the intended point of sales. A significant aspectof the method relates to a GRIN lens that can be fusion spliced to asingle mode optical fiber at a location behind the rear end of theferrule.

Aspects of the present disclosure allow ferrule assemblies to bemanufactured in large volumes at manufacturing locations where theprocess is most class effective. The ferrule assemblies, which are smallin size, can be effectively stripped in bulk to factory/assemblylocations closer to customer locations where the ferrule assemblies canbe spliced to fiber optic cables and a final connector assembly can takeplace. In this way, shipping of the cable itself (which tends to belarger in size and weight) can be minimized. Also, final assembly can bemade closer to customer locations thereby increasing lead times. Globalsupply chains can also be enhanced. From the foregoing detaileddescription, it will be evident that modifications and variations can bemade without departing from the spirit and scope of the disclosure.

In other embodiments, aspects of the present disclosure can be used withferrule-less connectors where the optical fiber stub is not supportedwithin a ferrule.

What is claimed is:
 1. A fiber optic cable and connector assemblycomprising: a ferrule having a front end and a rear end; a cable opticalfiber; an optical fiber stub having a first portion and a secondportion, the second portion projects rearwardly from the rear end of theferrule, the optical fiber stub having a constant mode field diameteralong its length, the optical fiber stub having a larger mode fielddiameter than the cable optical fiber; and a beam expanding fibersegment optically coupled between the cable optical fiber and theoptical fiber stub; wherein the first portion of the optical fiber stubis secured within a bore of the ferrule and the second portion of theoptical fiber stub is spliced to the beam expanding fiber segment at afirst splice; and wherein the beam expanding fiber segment is spliced tothe cable optical fiber at a second splice.
 2. The fiber optic cable andconnector assembly of claim 1, wherein a ferrule hub is positioned overthe rear end of the ferrule, over the beam expanding fiber segment andover the first splice.
 3. The fiber optic cable and connector assemblyof claim 2, wherein the first splice is within 5 millimeters of the rearend of the ferrule.
 4. The fiber optic cable and connector assembly ofclaim 2, wherein the hub is over molded over the rear end of theferrule, over the beam expanding fiber segment and over the firstsplice.
 5. The fiber optic cable and connector assembly of claim 1,wherein the first splice is within 20 millimeters of the rear end of theferrule.
 6. The fiber optic cable and connector assembly of claim 1,further comprising a connector body at least partially containing theoptical fiber stub and the beam expanding fiber segment.
 7. The fiberoptic cable and connector assembly of claim 6, wherein the cable opticalfiber is part of a cable having a jacket and strength members, andwherein the strength members are anchored to the connector body.
 8. Thefiber optic cable and connector assembly of claim 1, wherein the beamexpanding fiber segment is a graduated index fiber.
 9. The fiber opticcable and connector assembly of claim 1, wherein the beam expandingfiber segment is a quarter pitch GRIN lens.
 10. The fiber optic cableand connector assembly of claim 1, wherein the beam expanding fiberincludes a pre-expansion fiber spliced to a primary expansion fiber. 11.The fiber optic cable and connector assembly of claim 1, wherein theoptic fiber stub is a step index fiber.
 12. The fiber optic cable andconnector assembly of claim 1, wherein the mode field diameter of theoptical fiber stub is at least 50% larger than the mode field diameterof the cable optical fiber.
 13. The fiber optic cable and connectorassembly of claim 1, wherein the optical fiber stub has a core diameterof at least 12 microns.
 14. The fiber optic cable and connector assemblyof claim 1, wherein the mode field diameter of the optical fiber stub isat least three times as large as the mode field diameter of the cableoptical fiber.
 15. The fiber optic cable and connector assembly of claim1, wherein the mode field diameter of the optical fiber stub is at leastfour times as large as the mode field diameter of the cable opticalfiber.
 16. The fiber optic cable and connector assembly of claim 1,wherein a core diameter of the optical fiber stub is at least 50% largerthan a core diameter of the cable optical fiber.
 17. A method for massproducing fiber optic connector assemblies including fiber opticconnectors connected to fiber optic cables, the fiber optic connectorsincluding ferrule assemblies having optical fiber stubs supported inferrules, the method comprising: manufacturing the ferrule assemblies ata first central location in volumes exceeding 1,000,000 of the ferruleassemblies per year; and distributing the ferrule assemblies from thefirst central location to a second regional location where the fiberoptic connector assemblies are mass produced by fusion splicing theoptical fiber stubs to beam expanding fiber segments, wherein the beamexpanding fiber segments are then fusion spliced to cable optical fibershaving mode field diameters that are smaller than mode field diametersof the optical fiber stubs.
 18. A method for mass producing fiber opticconnector assemblies including fiber optic connectors connected to fiberoptic cables, the fiber optic connectors including ferrule assemblieshaving optical fiber stubs supported in ferrules, the ferrule assembliesalso including beam expanding fiber segments spliced to rear ends of theoptical fiber stubs at locations rearwardly offset from rear ends of theferrules, the method comprising: manufacturing the ferrule assemblies ata first central location in volumes exceeding 1,000,000 of the ferruleassemblies per year; and distributing the ferrule assemblies from thefirst central location to a second regional location where the fiberoptic connector assemblies are mass produced by fusion splicing the beamexpanding fiber segments to cable optical fibers having mode fielddiameters that are smaller than mode field diameters of the opticalfiber stubs.
 19. A fiber optic cable and fiber assembly comprising: aferrule having a front end and a rear end; an expanded beam fibersegment having a front portion secured within the ferrule and a rearportion that projects rearwardly from the rear end of the ferrule; and afiber optic cable having a single mode optical fiber optically coupledto the expanded beam fiber segment at a splice location behind the rearend of the ferrule.